Struct DecayEngine 

pub struct DecayEngine {
    pub multiplier: f32,
}

Decay engine — computes current retention scores for memory entries.

Uses an Ebbinghaus-inspired forgetting curve with adjustments for:

• Memory type (UserProfile decays slower than Conversation)
• Protection level (Higher protection = slower decay)
• Access frequency (Frequently accessed = slower decay)
• Global multiplier (user-configurable)

Fields

multiplier: f32

Global decay multiplier. 1.0 = default speed.

Implementations

impl DecayEngine

pub fn new(multiplier: f32) -> DecayEngine

Create a new decay engine with the given multiplier.

pub fn default_engine() -> DecayEngine

Create with default multiplier (1.0).

pub fn compute_decay(&self, entry: &MemoryEntry, now: DateTime<Utc>) -> f32

Compute current decay score for an entry.

Returns a value between 0.0 (fully decayed) and 1.0 (fresh). Permanent protection always returns 1.0.

pub fn effective_importance(entry: &MemoryEntry) -> f32

Compute effective importance of a memory entry.

Effective importance = base_importance × (1 + ln(1 + access_count)) × decay_score.

pub fn is_prunable( &self, entry: &MemoryEntry, threshold: f32, now: DateTime<Utc>, ) -> bool

Check if an entry should be considered for pruning.

An entry is a pruning candidate when:

• its current decay score (recomputed at now) < threshold
• protection is None or Low
• not pinned
• not auto-protected type

The decay is recomputed against now rather than reading the stale persisted entry.decay_score, so an entry that has crossed the threshold since the last Dream run is still detected.

Trait Implementations

impl Clone for DecayEngine

fn clone(&self) -> DecayEngine

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DecayEngine

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.